The present invention relates to a device for improving the performance of a portable engine-powered tool during winter conditions.
Portable engine powered tools are widely used for different kinds of work. The environmental conditions to which the tools are exposed can therefore vary greatly depending upon the type of tool, the season, and the climate of the region where the tool is used. It is therefore not possible to make tools that will perform ideally in every possible environment. For example, chainsaws are used almost everywhere in the world, from rainforests to forests in the far north. The air temperature can vary between several degrees below zero in combination with snow and up to very high temperatures during summertime in sunshine.
The considerable variation in temperature is one parameter that heavily affects the performance of the engine. The greatest problems occur when the temperature is low. Another parameter of great importance to engine performance is the humidity of the air. The combination of low temperature and a high humidity is devastating for the tool. When such cold humid air passes over passages and nozzles in the engine, it causes a temperature drop in the air, which in turn causes the water in the air to condensate and freeze into ice that blocks the passages and nozzles.
Another problem during wintertime use is snow. Powdery snow in combination with the above-described parameters is especially a problem since the snow can get into the tool. Heavy snow may block the air inlet to the tool""s engine, while lighter snow may be sucked into the air inlet with the air. Snow that has been sucked inside of the tool melts and then refreezes in the passages and nozzles causing them to be blocked.
Different approaches have been tried in order to find a solution to the above-described problems. One approach is to guide heated air from the engine""s exhaust through a channel inside the casing of the tool to the air inlet to compensate for the low temperature air in the surrounding. However, this approach has some drawbacks. First of all is it difficult to create a channel that will work properly inside the narrow casing without increasing the size or the casing. Secondly, the channel must be repeatedly opened and closed depending upon the surrounding conditions. This could either be done by providing a complicated device on the outside of the casing or by opening the casing and activating or deactivating the channel inside the casing. The last alternative is not desirable due to the risk of dropping parts while the casing is open, especially if there is a lot of snow. There is also a risk that equipment inside the casing will be damaged. Both of these alternatives are consequently quite complicated and there is a need for a simpler solution to the above-described problems.
The present invention solves the above-described problems by guiding heated air from the area around the muffler to the air inlet to the engine. This is done by first guiding the air through an opening in the casing and then through a channel placed on the outside of the casing. The channel ends before reaching the air inlet to the engine allowing the heated air to mix with the colder ambient air before being sucked into the engine. The temperature of the air mixture will then be high enough to prevent the water in the air from freezing in passages and nozzles inside the engine or the carburetor.
A channel placed on the outside of the casing has several advantages since it addresses the described problems in a simple way. The casing of the tool, such as a chainsaw, can be designed in a compact way, since the channel, or other arrangement for preheating the air for the engine, is not located inside the casing. If the chainsaw is used outside in winter conditions, the channel can be easily attached on the outside of the casing without risking damage or loss of components. The attached channel also serves to protect against snow getting into openings in the casing since the channel covers some of these openings. Another advantage of the present invention is that the area around the carburetor is also heated, which is favorable for the performance of the engine during winter conditions when the air temperature is low.
The channel is necessarily manufactured of a material that is strong and wear-resistant since the attached channel may be exposed to a lot of impact and wear. The weight of the channel is kept as low as possible in order to minimize the weight that must be carried by the operator. The channel may be secured to the casing by appropriate means depending upon the designs of the channel and the casing. One example is to secure the channel to the casing by using the same screws that secure different parts of the casing to each other. The channel could also be attached, for example, by providing the channel with hooks that can be attached to corresponding receiving means located on proper places on the casing. The above examples could be combined in order to further assist the operator in securing the channel to the casing.
The attachable channel on the outside of the casing of the present invention can also be designed to match older chainsaws already on the market which will make it possible to improve their performance during winter conditions.